Networks transfer electronic information between different locations. Broadband networks differ from other networks in that they transfer a relatively large amount of information during each unit of time. Future broadband networks are expected to convey video signals for business, educational and residential applications. Such networks may provide services such as broadcast-like video distribution, individual access to video program libraries, video telephone, video conferencing, and the like. Any one of such services may, for example, communicate signals having data transfer rates of up to 50 Mb/s or more.
In order to effectively serve a large number of customers, a broadband network includes switching nodes. At switching nodes, broadband signals are routed along selected paths so that desired signals are delivered from signal sources to targets.
Numerous problems are faced by a broadband, real-time switch that accommodates a large number of connections. These problems result, at least in part, from the high data transfer rates associated with broadband communications. In short, a tremendous amount of data need to be processed or otherwise transferred through the switch during every unit of time, and the larger the number of connections supported by the switch, the greater the amount of data which need to be processed.
Conventional signaling protocols are often implemented in communications networks to eliminate or simplify the design effort that would otherwise be required. Standard signaling protocols may also provide a measure of reliability and compatibility with other communications systems. Unfortunately, operating speed, efficiency and user-friendliness may be sacrificed when such conventional protocols are rigidly followed.
Conventional signaling protocols, such as Q.931, are not designed to efficiently accommodate broadcast-like video switching. When operating to provide broadcast-like video programming, a broadband network may be required to process numerous control messages from any number of customer locations. Any given customer location may include more than one television (or other receiving equipment) that can interact with the network to obtain video programming. Typically, each piece of customer receiving equipment is an independently signaled entity, i.e., there is no intercommunication between individual receivers located at the same customer location.
Networks that utilize conventional signaling protocols, such as the Q.931 protocol, may be incapable of supporting various user-friendly features. For example, conventional Q.931 signaling does not allow one receiving unit to "bridge" onto or "merge" with a video program currently being viewed at a first receiving unit without independently identifying the video program to the network switch. This feature may be desirable when, for example, a customer viewing an upstairs television set wishes to conveniently switch channels to view whatever program is currently being viewed at a downstairs television set.
Conventional signaling protocols identify video programs and other communication signals with identification codes, addresses, and/or subaddresses. Although the identity of a received video program may be known at the receiving unit communicating with the network switch, other receiving units located at the same customer premises do not have access to the program identity. When the video program is obtained from a remote video source through network interaction there may be no program identification at all. It may be difficult if not impossible to perform program bridging or merging under such circumstances.
Video program bridging or merging may be crudely realized by splitting a signal after it has been received at a first receiving unit. Unfortunately, control of the video program remains at the first receiving unit, and any interconnected receiving units become mere satellite viewing stations. For example, the bridged video program is not maintained at any other receiving units if the user switches video programs at the first receiving unit. Furthermore, the bridged video program is lost at all receiving units if the first receiving unit is shut down.